Adenovirus is a double-stranded DNA virus with a genome size of about 36 kilobases (kb), which has been widely used for gene transfer applications due to its ability to achieve highly efficient gene transfer in a variety of target tissues and large transgene capacity. Conventionally, E1 genes of adenovirus are deleted and replaced with a transgene cassette consisting of the promoter of choice, cDNA sequence of the gene of interest and a poly A signal, resulting in a replication defective recombinant virus.
Adenoviruses have a characteristic morphology with an icosahedral capsid consisting of three major proteins, hexon (II), penton base (III) and a knobbed fibre (IV), along with a number of other minor proteins, VI, VIII, IX, IIIa and IVa2 [W. C. Russell, J. Gen Virol., 81:2573-2604 (November 2000)]. The virus genome is a linear, double-stranded DNA with a terminal protein attached covalently to the 5′ terminus, which have inverted terminal repeats (ITRs). The virus DNA is intimately associated with the highly basic protein VII and a small peptide pX (formerly termed mu). Another protein, V, is packaged with this DNA-protein complex and provides a structural link to the capsid via protein VI. The virus also contains a virus-encoded protease, which is necessary for processing of some of the structural proteins to produce mature infectious virus.
A classification scheme has been developed for the Mastadenovirus family, which includes human, simian, bovine, equine, porcine, ovine, canine and opossum adenoviruses. This classification scheme was developed based on the differing abilities of the adenovirus sequences in the family to agglutinate red blood cells. The result was six subgroups, now referred to as subgroups A, B, C, D, E and F. See, T. Shenk et al., Adenoviridae: The Viruses and their Replication”, Ch. 67, in FIELD'S VIROLOGY, 6th Ed., edited by B. N Fields et al, (Lippincott Raven Publishers, Philadelphia, 1996), p. 111-2112.
Recombinant adenoviruses have been described for delivery of heterologous molecules to host cells. See, U.S. Pat. No. 6,083,716, which describes the genome of two chimpanzee adenoviruses. Simian adenoviruses, C5, C6 and C7, have been described in U.S. Pat. No. 7,247,472 as being useful as vaccine vectors. Other chimpanzee adenoviruses are described in WO 2005/1071093 as being useful for making adenovirus vaccine carriers.
What is needed in the art are effective vectors which avoid the effect of pre-existing immunity to selected adenovirus serotypes in the population.